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Handheld devices such as Personal Digital Assistants (PDAs), cellular phones, portable computing devices and other two-way data and/or voice communication devices, are increasing in popularity as they have become more feature-rich at an ever decreasing cost to the consumer. In particular, handheld devices that allow both voice and data communication are almost indispensable tools in certain businesses and government agencies. The need to maintain electronic mail communication as well as a variety of related information management applications such as electronic calendars, contacts and address books, without impeding mobility are among the critical factors driving the demand for handheld communication devices. Popular handheld devices include those supplied by Research In Motion Ltd. of Waterloo, Ontario, Canada.
However, some applications running on handheld devices may be cumbersome to use. This is partly due to the limitations of the hardware although user interface design also plays a part. Handheld devices must, by definition, be easily portable and convenient to carry around. This entails that the handheld devices must have a small form factor and a light enough weight for mobile use. Unfortunately, the small size of a mobile handheld device limits the available physical means for data entry, data output and general interaction with a user. Both the data entry pad or keyboard and viewable screen size of a handheld device are necessarily small compared with personal computers or workstations. Moreover, the use of a peripheral input device such as a mouse is awkward or impractical for handheld devices, as the peripheral is often almost as large as the handheld itself. In addition, handheld devices are often battery operated. Battery operated devices must pay particular attention to power consumption as power is a very limited resource. It is thus advantageous, for power conservation purposes, to minimize the number of components that consume power.
Therefore it is often challenging for applications running on handheld devices, to offer user interface features that are as rich and as convenient to use as those offered by their counterparts running on PCs and workstations. PCs have much larger screens, bigger keyboards and may easily use additional peripheral input devices such as a mouse. Conventional applications running on handheld devices thus typically offer user interfaces that are less familiar and may sometimes be confusing to use. Approaches to solve user interface problems have tended to focus on the design of small form-factor keyboard layouts for optimal thumb-based data entry, such as the solution taught by U.S. Pat. No. 6,867,763 granted to Research In Motion Ltd.
However, the visual aspects of data entry interfaces in handheld devices for common applications such as email client software, still tend to be different from those offered by the desktop equivalents, due primarily to the limitations of screen size. These differences in the user interfaces, between handheld versions and desktop versions of similar applications such as email clients are disadvantageous. The typical handheld user is almost always familiar with a desktop email client that offers a more convenient user interface; and is therefore likely to be inconvenienced by a user interface that is very different. Composing an email message using conventional email clients on handhelds, for instance, often entails an excessive use of menu driven input. Accordingly, there is a need for applications running on handheld devices that mimic some of the desirable aspects of user interfaces of corresponding desktop applications. Advantageously, a better user interface would make handheld devices more convenient and enjoyable to use.